Imaging system with electrophotographic patterning of an image definition material and methods therefor

ABSTRACT

A system comprises an electrophotographic subsystem, a transfer subsystem, an imaging member, and an inking subsystem. The electrophotographic subsystem comprises a photoreceptor, a charging subsystem, an exposure subsystem, and a development subsystem. In operation, the photoreceptor is charged areawise. An exposure pattern is formed by the exposure subsystem on the surface of the charged photoreceptor to thereby write a latent charge image onto the photoreceptor surface. The image is developed with an image definition material, such as a dampening fluid. The image definition material forms a positive pattern of the image to be printed. The image pattern is then transferred to the reimageable surface. The transferred pattern is then developed by selectively applying an ink over regions of image definition material. The inked image may be transferred to a substrate.

BACKGROUND

The present disclosure is related to marking and printing methods andsystems, and more specifically to methods and systems for variablymarking or printing data using lithographic and electrophotographicsystems and methods.

Offset lithography is a common method of printing today. (For thepurposes hereof, the terms “printing” and “marking” areinterchangeable.) In a typical lithographic process a printing plate,which may be a flat plate, the surface of a cylinder, or belt, etc., isformed to have “image regions” formed of hydrophobic and oleophilicmaterial, and “non-image regions” formed of a hydrophilic material. Theimage regions are regions corresponding to the areas on the final print(i.e., the target substrate) that are occupied by a printing or markingmaterial such as ink, whereas the non-image regions are the regionscorresponding to the areas on the final print that are not occupied bysaid marking material. The hydrophilic regions accept and are readilywetted by a water-based fluid, commonly referred to as a fountainsolution (typically consisting of water and a small amount of alcohol aswell as other additives and/or surfactants to reduce surface tension).The hydrophobic regions repel fountain solution and accept ink, whereasthe fountain solution formed over the hydrophilic regions forms a fluid“release layer” for rejecting ink. Therefore the hydrophilic regions ofthe printing plate correspond to unprinted areas, or “non-image areas”,of the final print.

The ink may be transferred directly to a substrate, such as paper, ormay be applied to an intermediate surface, such as an offset (orblanket) cylinder in an offset printing system. The offset cylinder iscovered with a conformable coating or sleeve with a surface that canconform to the texture of the substrate, which may have surfacepeak-to-valley depth somewhat greater than the surface peak-to-valleydepth of the imaging plate. Also, the surface roughness of the offsetblanket cylinder helps to deliver a more uniform layer of printingmaterial to the substrate free of defects such as mottle. Sufficientpressure is used to transfer the image from the offset cylinder to thesubstrate. Pinching the substrate between the offset cylinder and animpression cylinder provides this pressure.

In one variation, referred to as dry or waterless lithography ordriography, the plate cylinder is coated with a silicone rubber that isoleophobic and physically patterned to form the negative of the printedimage. A printing material is applied directly to the plate cylinder,without first applying any fountain solution as in the case of theconventional or “wet” lithography process described earlier. Theprinting material includes ink that may or may not have some volatilesolvent additives. The ink is preferentially deposited on the imagingregions to form a latent image. If solvent additives are used in the inkformulation, they preferentially diffuse towards the surface of thesilicone rubber, thus forming a release layer that rejects the printingmaterial. The low surface energy of the silicone rubber adds to therejection of the printing material. The latent image may again betransferred to a substrate, or to an offset cylinder and thereafter to asubstrate, as described above.

The above-described lithographic and offset printing techniques utilizeplates which are permanently patterned, and are therefore useful onlywhen printing a large number of copies of the same image (long printruns), such as magazines, newspapers, and the like. Furthermore, they donot permit creating and printing a new pattern from one page to the nextwithout removing and replacing the print cylinder and/or the imagingplate (i.e., the technique cannot accommodate true high speed variabledata printing wherein the image changes from impression to impression,for example, as in the case of digital printing systems). Furthermore,the cost of the permanently patterned imaging plates or cylinders isamortized over the number of copies. The cost per printed copy istherefore higher for shorter print runs of the same image than forlonger print runs of the same image, as opposed to prints from digitalprinting systems.

Lithography and the so-called waterless process provide very highquality printing, in part due to the quality and color gamut of the inksused. Furthermore, these inks—which typically have a very high colorpigment content (typically in the range of 20-70% by weight)—are verylow cost compared to toners and many other types of marking materials.Thus, while there is a desire to use the lithographic and offset inksfor printing in order to take advantage of the high quality and lowcost, there is also a desire to print variable data from page to page.Heretofore, there have been a number of hurdles to providing variabledata printing using these inks. Furthermore, there is a desire to reducethe cost per copy for shorter print runs of the same image.

One problem encountered is that offset inks have too high a viscosity(often well above 50,000 cps) to be useful in nozzle-based inkjetsystems. In addition, because of their tacky nature, offset inks havevery high surface adhesion forces relative to electrostatic forces andare therefore difficult to manipulate onto or off of a surface usingelectrostatics. (This is in contrast to dry or liquid toner particlesused in electrographic systems, which have low surface adhesion forcesdue to their particle shape and the use of tailored surface chemistryand special surface additives.)

Efforts have been made to create lithographic and offset printingsystems for variable data in the past. One example is disclosed in U.S.Pat. No. 3,800,699, incorporated herein by reference, in which anintense energy source such as a laser to pattern-wise evaporate afountain solution.

In another example disclosed in U.S. Pat. No. 7,191,705, incorporatedherein by reference, a hydrophilic coating is applied to an imagingbelt. A laser selectively heats and evaporates or decomposes regions ofthe hydrophilic coating. Next a water based fountain solution is appliedto these hydrophilic regions rendering them oleophobic. Ink is thenapplied and selectively transfers onto the plate only in the areas notcovered by fountain solution, creating an inked pattern that can betransferred to a substrate. Once transferred, the belt is cleaned, a newhydrophilic coating and fountain solution are deposited, and thepatterning, inking, and printing steps are repeated, for example forprinting the next batch of images.

In yet another example, a rewritable surface is utilized that can switchfrom hydrophilic to hydrophobic states with the application of thermal,electrical, or optical energy. Examples of these surfaces include socalled switchable polymers and metal oxides such as ZnO₂ and TiO₂. Afterchanging the surface state, fountain solution selectively wets thehydrophilic areas of the programmable surface and therefore rejects theapplication of ink to these areas.

High-speed inkjet printing is another approach currently utilized forvariable content printing. Special low-viscosity inks are used in theseprocesses to permit rapid volume printing that can produce variablecontent up to page-by-page content variation. High-speedelectrophotographic processes are also known.

However, there remain a number of problems associated with thesetechniques. For example, the process of selective evaporation ofdampening fluid requires a relatively high-powered, coherent radiationsource, which generates heat and consume undesirably large amount ofpower. Such high-powered radiation sources are also quite expensive.

High-speed inkjet systems and process rely on special low viscosity inksthat produce a non-standard final printed product. Such inks are alsolimited in the color ranges available. Further, such inks are relativelyquite costly.

High-speed electrophotographic systems and process require “liquidtoners” (electrophotography typically being a dry process). These liquidtoners are essentially charged toner particles suspended in aninsulating liquid. Producing an appropriate liquid toner thatappropriately balances color, ability to charge, cleanability, and lowcost has proven difficult.

Switchable coatings, especially the switchable polymers discussed above,are typically prone to wear and abrasion and expensive to coat onto asurface. Another issue is that they typically do not transform betweenhydrophobic and hydrophilic states in the fast (e.g., sub-millisecond)switching timescales required to enable high-speed variable dataprinting. Therefore, their use would be mainly limited to short-runprint batches rather than to truly variable data high speed digitallithography wherein every impression can have a different image pattern,changing from one print to the next.

SUMMARY

Accordingly, the present disclosure addresses the above problems, aswell as others, enabling the printing of variable content withoutcomplex toners and supporting systems. The present disclosure isdirected to systems and methods for providing hybrid electrophotographyand lithography.

A system according to one embodiment of the present disclosure comprisesan electrophotographic subsystem, a transfer subsystem, an imagingmember, and an inking subsystem. The electrophotographic subsystemcomprises a photoreceptor, a charging subsystem, an exposure subsystem,and in numerous embodiments a development subsystem.

In operation, the photoreceptor is charged areawise. A light beam fromthe exposure subsystem is then scanned and pulsed onto the surface ofthe charged photoreceptor to thereby write a charge pattern representinga latent positive image (the same as the final ink image to be appliedto a substrate) onto the photoreceptor surface.

In certain embodiments, the latent charge is developed with an imagedefinition material, such as a liquid or dry toner, that is itselfcharged (or contains charged particles) in such a manner as to beattracted to the latent charge regions on the photoreceptor surface. Inthe case of a liquid, the image definition material may function as adampening fluid that is preferentially attractive to ink (“ink-philic”)applied in subsequent steps. In certain embodiments disclosed herein,the liquid and any particles therein have no pigmentation, although weinterchangeably refer to the liquid as an image definition material anddampening fluid herein. In the case of dry toner, the image definitionmaterial may form an ink-attractive (“ink-philic”) pattern that also ispreferentially attractive to ink applied in subsequent steps. It will beappreciated that while we refer to a material as toner in the presentdisclosure, this reference is for convenience and clarity, and non-toneror toner-like particulate materials that provide the same or similarfunctionality are within the scope of the present disclosure.

A positive pattern of the image to be printed may therefore be formed ofimage definition material on the photoreceptor surface. This positiveimage is then transferred to the reimageable surface. The positive imageis then developed over the reimageable surface with an ink havingdesirable properties such as having an appropriate color, providing adesirable final surface quality, having a low cost, beingenvironmentally benign, and so on. The reimageable surface may be highlyink rejective (“ink-phobic”) as compared to the image definitionmaterial, such that the ink is preferentially disposed over the imagedefinition material. Ink is rejected by the reimageable surface, or by asegregation material deposited thereover, in the regions where no imagedefinition material resides.

The inked image is then transferred to a substrate at a nip roller orthe like, preferentially splitting from at least some of the imagedefinition material to the substrate. An optional cleaning subsystemwill remove any residual image definition material and/or segregationmaterial on the imaging member that does not otherwise evaporate, aswell as any residual ink, readying the imaging member for a nextprinting pass. Post printing, liquid image definition materialtransferred to the substrate may quickly evaporate, leaving the inkedimage. Optionally, image definition material transferred with the ink tothe substrate may provide a desired surface quality or functionality tothe ink image, such as controlling material viscosity, deliveringadditives (e.g., photo-curing or thermal-curing agents, fixing agents,etc.), reflectivity (e.g., gloss), mechanical strength, waterproofing,texture, adding encoding material (e.g., magnetic or electrostaticallychargeable particles), and so on. Certain of these qualities/functionsmay be realized by heating or cooling the inked image on the substrate,by reaction with the substrate, and so on.

Magnetic particles (either paramagnetic or having a permanent magneticmoment) such as those used in magnetic inks and toner for magnetic inkcharacter recognition (MICR) applications may be used with the resultantproperty that they can be extracted from the surface of the ink using astrong magnetic field. The magnetic particles can be made of iron oxidesor similar materials and, in liquid carriers, the particles can besub-micron in diameter and transparent in the visible wavelengths. Thus,cleaning of the magnetic toner may be accomplished, for example, bypassing the surface through a sufficiently strong magnetic field suchthat the magnetic particles are pulled from the surface, where they canthen be recycled or disposed.

In an alternate embodiment, the image definition material wets the ink.It may be relatively hydrophobic (as is the ink) and the reimageablesurface relatively hydrophilic. In this embodiment, the image definitionmaterial may be assisted in at least temporarily adhering to (wetting)the reimageable surface by different techniques, such as applying acounter-charge to assist in transferring the fluid to the reimageablesurface, utilizing a bifunctional surfactant that is hydrophilic on oneend and hydrophobic on other end, and so on. Field assist, compositionof the reimageable surface, etc. may also be employed to affect transferto substrate. Following transfer of the image definition material to theimaging member, a segregation material layer (e.g., water or awater-based solution) is applied over the imaging member, with theresult being segregation material disposed in regions where no imagedefinition material resides over the imaging member. Ink, of a type thatis rejected by the segregation material, (e.g., that is relativelyhydrophobic) is applied such that it preferentially resides over theimage definition material. The ink is then transferred to a substrate ata transfer nip. Some volume of image definition material may transfer tothe substrate with the ink. Again, this may be advantageously controlledto provide a desired surface finish, fixing of the ink to the substrate,viscosity control, delivery of additives (e.g., photo-curing orthermal-curing agents) to the inked image, etc. Some volume of thesegregation material may also transfer to the substrate with the ink,although it may quickly evaporate from the substrate surface.

In still another embodiment, a latent positive image of image definitionmaterial is formed on the photoreceptor surface as above. The latentimage is then developed with ink while still on the photoreceptor. Theink has an affinity for the image definition material as compared to thephotoreceptor surface, and therefore forms an inked image correspondingto the image formed by the image definition material. The inked image istransferred to an imaging member with or without the image definitionmaterial. Electrostatics or other mechanisms may be used to separate orstratify the ink and the image definition material prior to transfer tothe substrate.

According to still further embodiments, a relatively uniform imagedefinition material layer is deposited over the reimageable surface. Alatent charge pattern is formed at the surface of the photoreceptor, aspreviously described. The image forming material has an affinity (e.g.,electrostatic) for the photoreceptor where the charge is present,causing image definition material to be removed from the surface of theimaging member in locations corresponding to charged areas of thephotoreceptor. Ink is then developed over the image definition material,and the inked image transferred to the substrate, essentially aspreviously discussed. Optionally, a segregation material such as wateror a similar fluid may be introduced between areas of image formingmaterial to assist with ink image definition.

According to yet another embodiment, a relatively uniform layer ofsegregation material (e.g., water) is deposited over the reimageablesurface. A latent charge pattern is formed at the surface of thephotoreceptor, and developed with image definition material, aspreviously described. The image definition material is transferred tothe reimageable surface such that it at least partially embeds in thesegregation material layer. Optionally, the electrostatic charge stateof the image definition material and the reimageable surface may beemployed to assist with the affinity of the image definition material tothe reimageable surface. Ink is then developed over the image definitionmaterial, and the inked image transferred to the substrate, essentiallyas previously discussed.

The above is a summary of a number of the unique aspects, features,advantages, and embodiments of the present disclosure. However, thissummary is not exhaustive. Thus, these and other aspects, features, andadvantages of the present disclosure will become more apparent from thefollowing detailed description and the appended drawings, whenconsidered in light of the claims provided herein.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings appended hereto like reference numerals denote likeelements between the various drawings. While illustrative, the drawingsare not drawn to scale. In the drawings:

FIG. 1 is a side view of a system for variable lithography according toan embodiment of the present disclosure.

FIGS. 2A and 2B are side-view, cut-away illustrations of a mechanism forselectively applying image definition material to a surface of aphotoreceptor according to one embodiment of the present disclosure.

FIG. 3 is a side-view, cut-away illustration of a mechanism fortransferring an image definition material image to the surface of animaging member according to one embodiment of the present disclosure.

FIG. 4 is a side view of a system for variable lithography according toanother embodiment of the present disclosure.

FIG. 5 is a side view of a system for variable lithography according toyet another embodiment of the present disclosure.

FIG. 6 is a flow diagram illustrating an embodiment of operation of asystem for variable lithography for example of the type shown in FIG. 1,4 or 5.

FIG. 7 is a side view of a system for variable lithography according toa further embodiment of the present disclosure.

FIG. 8 is a flow diagram illustrating an embodiment of operation of asystem for variable lithography for example of the type shown in FIG. 7.

FIG. 9 is a side view of a system for variable lithography according toa still further embodiment of the present disclosure.

FIG. 10 is a flow diagram illustrating an embodiment of operation of asystem for variable lithography for example of the type shown in FIG. 9.

FIG. 11 is a side view of a system for variable lithography according tostill another embodiment of the present disclosure.

FIG. 12 is a flow diagram illustrating an embodiment of operation of asystem for variable lithography for example of the type shown in FIG.11.

DETAILED DESCRIPTION

We initially point out that description of well-known startingmaterials, processing techniques, components, equipment and otherwell-known details are merely summarized or are omitted so as not tounnecessarily obscure the details of the present disclosure. Thus, wheredetails are otherwise well known, we leave it to the application of thepresent disclosure to suggest or dictate choices relating to thosedetails.

With reference to FIG. 1, there is shown therein a system 10 forelectrophotographic patterning of an image definition material accordingto one embodiment of the present disclosure. System 10 comprises animaging member 12, in this embodiment a drum, but may equivalently be aplate, belt, etc., surrounded by a number of subsystems described indetail below. Imaging member 12 applies an ink image to substrate 14 atnip 16 where substrate 14 is pinched between imaging member 12 and animpression roller 18. A wide variety of types of substrates, such aspaper, plastic or composite sheet film, ceramic, glass, etc. may beemployed. For clarity and brevity of this explanation we assume thesubstrate is paper, with the understanding that the present disclosureis not limited to that form of substrate. For example, other substratesmay include cardboard, corrugated packaging materials, wood, ceramictiles, fabrics (e.g., clothing, drapery, garments and the like),transparency or plastic film, metal foils, etc. A wide latitude ofmarking materials may be used including those with pigment densitiesgreater than 10% by weight including but not limited to metallic inks orwhite inks useful for packaging. For clarity and brevity of this portionof the disclosure we generally use the term ink, which will beunderstood to include the range of marking materials such as inks,pigments, and other materials, which may be applied by systems andmethods, disclosed herein.

In one embodiment, imaging member 12 comprises a thin reimageablesurface layer 20 formed over a structural mounting layer (for examplemetal, ceramic, plastic, etc.), which together forms a rewriteableprinting blanket. Additional structural layers, such as an intermediatelayer (not shown) below reimageable surface layer 20 may be electricallyinsulating (or conducting), thermally insulating (or conducting), havevariable compressibility and durometer, and so forth. In one embodiment,an intermediate layer is composed of closed cell polymer foam sheets andwoven mesh layers (for example, cotton) laminated together with verythin layers of adhesive. Typically, blankets are optimized in terms ofcompressibility and durometer using a 3-4 ply layer system that isbetween 1-3 mm thick with reimageable surface layer 20 designed to haveoptimized texture, toughness, and surface energy properties.

Reimageable surface layer 20 may take the form of a stand-alone drum orweb, or a flat blanket wrapped around a cylinder core. In anotherembodiment the reimageable surface layer 20 is a continuous elasticsleeve placed over a cylinder core. Flat plate, belt, and webarrangements (which may or may not be supported by an underlying drumconfiguration) are also within the scope of the present disclosure. Forthe purposes of the following discussion, it will be assumed thatreimageable surface layer 20 is carried by a cylinder core, although itwill be understood that many different arrangements, as discussed above,are contemplated by the present disclosure.

According to various embodiments disclosed herein, reimageable surfacelayer 20 should be of a material that rejects wetting with the ink(i.e., “ink-phobic”). Reimageable surface layer 20 should also be of amaterial that provides relatively good adhesion and/or wetting of theimage definition material (discussed further below). Various examplesinclude polytetrafluoroethylene (PTFE, or Teflon) and fluorinatedsilicone surface layers, when used with water-based inks or other inkswith relatively high surface energies.

A photo-responsive photoreceptor 22 is charged by an appropriatemechanism 24, such as a corona discharge device, to have a first chargepolarity. Charged photoreceptor 22 is then exposed, such as by lightfrom a laser or LED array source 26. In the case of a laser, source 26is both pulsed, such as by a controller (not shown) and scanned, such asby a raster output scanner (ROS) subsystem (not shown). In the case ofan LED array or light bar, the individual elements comprising the arrayare modulated to produce the desired exposure pattern line-by-line. Byway of exposure, the scanned and pulse beam or pulsed linear arraycreates a latent charge image on the surface of photoreceptor 22.

It is understood that for the purposes of this disclosure, the term“light” is used to refer to wavelengths of electromagnetic radiation forexposure of photoreceptor 22. As used herein, “light” may be any of awide range of wavelengths from the electromagnetic spectrum, whethernormally visible to the unaided human eye (visible light), ultraviolet(UV) wavelengths, infrared (IR) wavelengths, micro-wave wavelengths, andso on.

An image definition material is then applied to the latent image on thesurface of photoreceptor 22 by an image definition material subsystem28. In one implementation in which the image definition material is aliquid, image definition material subsystem 28 comprises a series ofrollers 30 (referred to as a dampening unit) for uniformly wetting thesurface of photoreceptor 22 with an image definition material 31 fromreservoir 32. It is well known that many different types andconfigurations of dampening units exist. For example, spray systems,condensation systems, extrusion systems, and so on may alternatively beemployed. The purpose of the dampening unit is to deliver a controlledthickness of image definition material 31 on regions of photoreceptor 22defined by the latent charge image over unexposed (charged) regions ofthe photoreceptor. As will be explained further below, the imagedefinition material may comprise a liquid toner. Therefore, liquid tonerdelivery subsystems may also be employed as the image definitionmaterial subsystem 28.

The image definition material applied by image definition materialsubsystem 28 essentially takes the place of toner in a typicalelectrophotographic process. According to one embodiment, the imagedefinition material has certain properties rendering it both aneffective electrophotographic printing material and an ink-philiclithographic image definition material. The image definition materialmay comprise a carrier fluid that includes a toner-like chargeablematerial, such as organic/inorganic compact particles or dendriticallyshaped brushes, polymers or aggregates, iron oxide (magnetic), or metalor dielectric or other particles. In certain embodiments discussedherein, the particles may also have a surface quality and compositionsuch that they provide a desired degree of (either a significant amountor specifically as little as possible) liquid drag within the carrierfluid. Many materials are suitable as long as the material can carryelectrostatic charge. It should be noted that fewer requirements on theink composition exist in the current application so less expensivematerials can be used. In one embodiment, polymer aggregate furthercomprises charge control agents. The polymer material may be partiallycross-linked to provide a plurality of aggregates.

The particles may be dispersed in a carrier fluid. In one embodiment,the carrier fluid is insulative. Examples include (but are not limitedto) oils, or fluorosolvents such as Isopar™ (synthetic isoparaffin, fromExxon Mobil, Inc.), and the like. A surfactant monolayer is one example.It could either: bind to oleophobic reimageable surface and bind oilbased ink, or bind to hydrophobic reimageable surface and bind waterbased ink. It is also useful, again for reasons discussed further below,that carrier fluid be relatively cohesive. Materials used as an inkvehicle in liquid electrophotography may be considered. The carrierfluid with particles may be formulated as a low solid content, colorlessliquid “toner”. Optionally, the carrier fluid may include additives forimage fixing, providing a desired image finish (e.g., gloss), viscositycontrol, thermal- and/or photo-curing agents, etc.

According to one embodiment of the present disclosure, the particles inthe image definition material are provided with a second charge (i.e.,of a second charge polarity). This charge is of opposite sign (polarity)to the charge applied to the photoreceptor 22. The particles may becharged as a step in the process of forming the image definitionmaterial, e.g. triboelectrically or by zeta potential formation, or maybe charged in situ prior to application such as by a charging device 25.

Areas of photoreceptor 22 that are not exposed by light source 26 remaincharged, and the particles in the image definition material areselectively attracted thereto. Thus, as a second consequence theparticles are more strongly attracted to the photoreceptor in theseregions. (In an alternative embodiment, the particles are uniformlydispersed in the image definition material and can arrive more quicklyat the attracting regions of the photoreceptor.) The particles migratetoward the charged region of photoreceptor 22, dragging carrier fluidwith them. As the photoreceptor leaves the nip with roller 30, carrierfluid splits providing a net fluid thickness on the photoreceptorsurface greater than the thickness of adhering toner particles. Overregions of the photoreceptor that have been exposed by light source 26(discharged regions), image definition material will be repelled by thenature of the photoreceptor surface (e.g., high interface energy betweenthe photoreceptor surface and the image definition material), leavingthose regions over the surface of photoreceptor 22 without imagedefinition material. In certain cases, motion of the particles may alsocarry fluid away from regions that have been exposed by light source 26.This causes a splitting of the image definition material at the deliveryroller 30, with fluid preferentially transferring to the photoreceptorover charged regions, and remaining on the delivery roller overuncharged regions. (The splitting may not be complete, but will besufficient to provide image pattern formation, as discussed furtherbelow.)

Alternatively, precharging of reimageable surface 20 may be employed toattract oppositely charged particles thereto. In this case, the imagedefinition material minimally wets the particles. After the toner on thereimageable surface binds the ink and transfers the ink, the particlesremaining bound to reimageable surface 20 are charge-neutralized, forexample by a scorotron 53 (or similar mechanism). The residual toner isthen cleaned from the surface at 54.

Some or all of the carrier fluid may evaporate from the toner solutionprior to transfer of the ink to substrate 14. The greater the amount ofthe fluid that evaporates, the greater the surface properties of theparticles determine the wettability to the ink.

The process of developing the image definition material on the surfaceof photoreceptor 22 is illustrated in the example shown in FIGS. 2A and2B. With reference to FIG. 2A, a region 35 of photoreceptor 22 has beenexposed to light, thereby discharging that region. An adjacent region 37has not been exposed, and therefore retains the initial charge appliedto the photoreceptor. As image definition material 31 is broughtproximate the surface of photoreceptor 22, particles 33 (or ionicspecies) are attracted to photoreceptor 22 in regions 37. The particlescarry with them excess carrier fluid, thereby creating an imagedefinition material region 36.

With reference to FIG. 2B, in regions over exposed portions ofphotoreceptor 22, where charge has been dissipated, image definitionmaterial 31 will be less attracted to photoreceptor 22, and will remainon roller 30. Roller 30 may be provided with a surface charge density(e.g., repulsive to the charge in region 37) to assist with thispreferential transfer mechanism. In addition or as an alternative, thecomposition of the surface of photoreceptor 22 may be further selectedto repel image definition material 31 absent any electrostaticattraction, to thereby improve the selectivity of this mechanism forforming regions 36.

One mechanism for electrostatically enhanced image definition materialretention has been described above. However, many different mechanismsare possible, and the precise mechanism by which image definitionmaterial attaches to or is rejected by the photoreceptor does not form alimitation of the claims unless otherwise recited in those claims.

Returning to FIG. 1, the result of the aforementioned process is thatnumerous regions 36 are provided on the surface of photoreceptor 22,separated by regions 38 that are generally absent of image definitionmaterial. However, in certain embodiments, some residual imagedefinition material may remain in regions 38 over unexposed regions ofphotoreceptor 22. This residual image definition material will form arelatively much thinner region (in cross-section) as compared withadjacent fluid regions remaining over exposed regions of photoreceptor22. For example, in one embodiment regions 36 are on the order of 0.2 μmto 1.0 μm thick (and very uniform without pin holes), while residualimage definition material regions 38 may be on the order of less than0.1 μm. Thinner liquid regions require more force to split and thereforethe adhesion to the reimageable surface 20 can be insufficient totransfer residual image definition material regions 38, yet strongenough to split regions 36. Provided that there is a contrast betweenthe amount of the fluid present over exposed and non-exposed areas ofthe photoreceptor, a latent liquid image can nonetheless be formed whichmanifests in more or less fluid on the photoreceptor. Areas where athinner layer of fluid is present can be evaporated or dried if desiredby areawise heating by heating element 34. The latent negative image onphotoreceptor 22 may then be transferred to reimageable surface 20 attransfer point 40.

As the relative motions of photoreceptor 22 and imaging member 12proceed, image definition material regions 36 are transferred from thesurface of photoreceptor 22 to reimageable surface 20. In one mechanism,the image definition material wets the reimageable surface, and due tothe nature of reimageable surface 20 a portion of the image definitionmaterial transfers thereto. While some fluid may remain on photoreceptor22 after transfer of the majority thereof to reimageable surface 20, andindeed some fluid in regions 38 may also be transferred, the relativevolume and hence height above reimageable surface 20 of the transferredregions 38 will be sufficient to retain adequate contrast between theamount of the fluid in regions 36 and in regions 38 such that a liquidimage is formed on reimageable surface 20.

According to another embodiment of the present disclosure, illustratedin FIG. 3, charged particles in the image definition material are againused, this time to assist with the transfer of the image definitionmaterial from photoreceptor 22 to reimageable surface 20. In thisembodiment, pre-charging or biasing reimageable surface 20, for exampleby charging device 42, may aid transfer of image definition materialfrom photoreceptor 22 to reimageable surface 20. For example, ifreimageable surface 20 is provided with an increased attractive chargeto the image definition material as compared to regions 37 ofphotoreceptor 22, the image definition material will preferentially beattracted to reimageable surface 20. Due to surface tension, affinity ofthe image definition material to the surface of layer 20, and theaforementioned electrostatic attraction, the image definition materialof regions 36 will wet the reimageable surface 20 where the two comeinto contact at transfer point 40. The image definition material willsplit as the photoreceptor and imaging member 12 rotate relative to oneanother, transferring substantially the entirety of image definitionmaterial regions 36 from photoreceptor 22 to reimageable surface 20. Anyimage definition material remaining on photoreceptor 22 may be removedor allowed to evaporate prior to the next cycle of charging anddeveloping the photoreceptor.

Returning to FIG. 1, according to another embodiment of the presentdisclosure, the viscosity of the image definition material may beintentionally increased, particularly on the exposed surface oppositethe surface of photoreceptor 22, so as to increase its adhesion toreimageable surface 20. In addition to its role in evaporating excessresidual image definition material, heating element 34 may also serve topartially dry image definition material regions 36, transforming them toa higher viscosity or even semi-solid state. The viscosity of the fluidin regions 36 is thereby increased, particularly at exposed surfaces,and accordingly regions 36 tend to selectively adhere to reimageablesurface 20 at transfer point 40.

The latent image formed by regions 36 now resident on reimageablesurface 20 is next inked by inking subsystem 46. Inking subsystem 46 mayconsist of a “keyless” system using an anilox roller to meter offset ink56 onto one or more forming rollers. Alternatively, inking subsystem 46may consist of more traditional elements with a series of meteringrollers that use electromechanical keys to determine the precise feedrate of the ink. The general aspects of inking subsystem 46 will dependon the application of the present disclosure, and will be wellunderstood by one skilled in the art.

In order for ink 56 from inking subsystem 46 to selectively wet overregions 36, the ink must have sufficiently high adhesion to imagedefinition material 31, and low enough cohesive energy to split ontoregions 36 (and not into ink repelling regions 48). Furthermore, imagedefinition material 31 must have sufficient adhesion to the reimageablesurface 20, either due to surface wetting or external forces such aselectrostatic or magnetic, to remain attached to surface 20 duringinking and preferably during transfer. The adhesion can be reducedduring or after transfer by oil expression or removal or reversal ofelectrostatic or magnetic forces. In embodiments in which the imagedefinition material is a image definition material, the image definitionmaterial may be relatively tacky such that ink applied by inkingsubsystem 46 selectively adheres to the fluid. The ink composition maybe selected such that it preferentially adheres to or mixes with theimage definition material. In certain embodiments, the reimageablesurface may be made to be ink-phobic. For example, the ink may includeor be admixed with water, and reimageable surface 20 made to behydrophobic.

According to another embodiment 60, illustrated in FIG. 4, followingtransfer of region 36 of image definition material 31, a segregationmaterial subsystem 62 deposits a segregation material 64 overreimageable surface 20 in regions 48. Segregation material 64 isink-phobic such that ink deposited by inking subsystem 46 is rejectedover material 64. In one embodiment, segregation material 64 is water ora water-based solution. Optionally, the material comprising reimageablesurface 20 may be chosen to be hydrophilic and/or image definitionmaterial 31 chosen to be hydrophobic, thereby assisting in the selectivedeposition of segregation material 64 in regions 48 (i.e., betweenregions 36 of image definition material 31).

The ink 56 applied by inking subsystem 46 may be selected to behydrophobic, thereby increasing the contrast between regions over imagedefinition material regions 36 intended to be inked and regions 48intended to be non-inked. There are somewhat conflicting requirements ofthe ink at this point. On one hand, the ink should have a sufficientlyhigh viscosity that it selectively adheres to regions 36. On the otherhand, the ink should have a sufficiently low viscosity that isrelatively easily flows over and fully covers the surface of regions 36.Accordingly, the rheology of the ink may be adjusted for desiredproperties for example by adding a small percentage of a low molecularweight monomer or a lower viscosity oligomer to the ink. The inkrheology may also be controlled by selectively heating the ink withininking subsystem 46.

Returning to FIG. 1, ink 56 over regions 36 is next transferred tosubstrate 14 at transfer subsystem 50. In this embodiment, this isaccomplished by passing substrate 14 through nip 16 between imagingmember 12 and impression roller 18. Adequate pressure is applied betweenimaging member 12 and impression roller 18 such that the ink is broughtinto physical contact with substrate 14. Adhesion of the ink tosubstrate 14 and strong internal cohesion cause the ink to separate fromimage definition material regions 36, at least in part, and adhere tosubstrate 14. Impression roller or other elements of nip 16 may becooled to further enhance the transfer of the inked latent image tosubstrate 14. Indeed, substrate 14 itself may be maintained at arelatively colder temperature than the ink on imaging member 12, orlocally cooled, to assist in the ink transfer process.

Some image definition material may also transfer to substrate 14 andseparate from reimageable surface 20. In cases where the imagedefinition material comprises a liquid, the volume of this imagedefinition material transferred will be minimal, and it will rapidlyevaporate or be absorbed within the substrate. Optimal charge onsurfaces 20 and substrate 14 and the electrostatic interaction with theparticles in the image definition material can be set either to reduceor enhance transfer of the image definition material to substrate 14.

Alternatively, it is within the scope of this disclosure that an offsetroller (not shown) may first receive the ink image pattern, andthereafter transfer the ink image pattern to a substrate, as will bewell understood to those familiar with offset printing. Other modes ofindirect transferring of the ink pattern from imaging member 12 tosubstrate 14 are also contemplated by this disclosure.

Following transfer of the majority of the ink to substrate 14, anyresidual ink and residual image definition material may be removed fromreimageable surface 20, preferably without scraping or wearing thatsurface. In cases where the image definition material is an imagedefinition material, most of the image definition material can be easilyremoved quickly by using an air knife 52 with sufficient airflow.However some amount of ink residue may still remain. Removal of thisremaining ink may be accomplished in a variety of ways, such as by acleaning subsystem 54 of the type disclosed in the aforementioned U.S.application for letters patent Ser. No. 13/095,714.

With reference to FIG. 5, another embodiment 70 of the presentdisclosure is illustrated. According to embodiment 70, in addition toelements previously described, a segregation fluid subsystem 72 isdisposed proximate photoreceptor 22 such that a segregation fluid 74 maybe deposited over the surface of photoreceptor 22. Segregation material74 is selected to be ink-phobic. In one embodiment, segregation material74 is water or a water-based solution.

In operation, photoreceptor 22 is charged then patterned by light source26. Image definition material is deposited over the surface ofphotoreceptor 22 selectively over regions not exposed by light source26. This produces regions 76 in which no image definition material isdeposited over the surface of photoreceptor 22. As photoreceptor 22rotates past segregation fluid subsystem 72, segregation material 74 isdeposited preferentially in regions 76. Optionally, the surface ofphotoreceptor 22 may be temporarily or permanently hydrophilic and/orimage definition material 31 chosen to be hydrophobic, thereby assistingin the selective deposition of segregation material 74 in regions 76(i.e., between regions of image definition material 31). Inking of theimage definition material and transfer of the inked image to substrate14 may then proceed as previously discussed.

While in the preceding sections of this disclosure segregation materialwas illustrated as being deposited from a roller mechanism, many othermechanisms may equivalently server to selectively deposit segregationmaterial. For example, a spray system may uniformly spray thesegregation material over the reimageable surface 20 (e.g., embodiment60 of FIG. 4) or the surface of the photoreceptor 22 (e.g., embodiment70, FIG. 5). Alternatively, a nozzle system may be used to ejectdroplets of the segregation material over the target surface.Furthermore, in various embodiments the segregation material may bedeposited pattern-wise over the target surface to match the spacingsbetween the pattern of image forming material formed by image formingmaterial subsystem 28 (e.g., selective droplet ejection similar toink-jet printing). It will therefore be appreciated that segregationmaterial may be deposited by a wide variety of techniques, and thepresent disclosure shall not be interpreted as being limited to any onesuch technique.

Accordingly, a complete hybrid system and process is disclosed in which,with reference to FIG. 6, a charged photoreceptor is patterned at 102and developed at 104 from image definition material utilizing certainaspects of an electrophotography system and process, to form a latentpositive of the image to be printed. The latent image of imagedefinition material is transferred at 106 to an imaging member. Asegregation material is optionally introduced either uniformly over thereimageable surface before or after transfer of the image definitionmaterial (optional steps are shown in dashed outline) at 107. The imagedefinition material image (with or without segregation material) isinked on the surface of the imaging member at 108. The inked image isthen transferred to a substrate at 110 utilizing certain aspects of avariable data lithography system and process.

With reference to FIG. 7, another embodiment 90 of the presentdisclosure is illustrated. According to this embodiment, inkingsubsystem 46 is disposed proximate photoreceptor 22 following thelocation of image definition material subsystem 28 in the direction ofmotion of photoreceptor 22. Inking subsystem 46 is disposed andconfigured to selectively deposit ink over regions 36 of image formingmaterial 31 over the surface of photoreceptor 22.

In a first variation of this embodiment, the ink disposed over regions36 of image definition material 31 is selectively transferred toreimageable surface 20, while image definition material 31 remains onthe photoreceptor and is subsequently removed, such as by a cleaningsubsystem 96. The image definition material is selected to be of a typethat evaporates relatively quickly. Any image definition material thattransfers with ink 56 to reimageable surface may evaporate shortly aftersuch transfer. Regions of ink 56 transferred to reimageable surface 20may then be transferred to substrate 14 at nip 16, as previouslydiscussed.

In another variation of this embodiment, ink 56 may intermix with theimage definition material 31 in regions 36 to form mixture regions 92.Mixture regions 92 are then transferred to reimageable surface 20, andultimately transferred to substrate 14. For both dry toner that issubsequently dampened before inking and liquid toner the toner can staywith the photoreceptor and be reused while the liquid splits. Manyliquids either wet the ink with some mixing and some fluids can bechosen which wet the ink but have very little uptake by the ink.

In yet another variation of this embodiment, the ink and imagedefinition material do not separate at photoreceptor 22, nor do theymix, but rather are deposited together on reimageable surface 20 withthe ink disposed between image definition material and reimageablesurface 20. Some of the image definition material 31 may have evaporatedprior to transfer to reimageable surface 20. Image definition materialthat did not evaporate prior to transfer may evaporate off ofreimageable surface 20, leaving ink 56 exposed for transfer to substrate14.

Optionally, in one or more of the above variations, an evaporationaccelerator, such as a heat source 94, may be disposed and configured toassist with evaporation of image definition material 31 prior totransfer nip 16. Also optionally in one or more of the above variations,a desired quantity or component of the image definition material mayremain with the ink over reimageable surface 20 and be transferred tosubstrate 14 to provide surface quality control, accelerate or assistfixing, and so forth.

Accordingly, another complete hybrid system and process is disclosed inwhich, with reference to FIG. 8, a charged photoreceptor is patterned at122 and developed at 124 from image definition material utilizingcertain aspects of a liquid electrophotography system and process, toform a latent positive of the image to be printed. Ink is appliedselectively over the latent image of image definition material at 126.One of the following options is next employed: the ink is transferred toan imaging member, separating from the image definition material in theprocess and leaving the image definition material substantiallyremaining on the photoreceptor, as 128 a; both the ink and the imagedefinition material are transferred to the reimageable surface, at 128b; or the ink and image definition material mix, and the mixture istransferred to the reimageable surface, at 128 c. Optionally, at leastsome of the image definition material may be removed, such as byevaporation, from either or both of the photoreceptor and thereimageable surface at 130. The inked image is then transferred to asubstrate at 132 utilizing certain aspects of a variable datalithography system and process.

According to another embodiment 160 illustrated in FIG. 9, an imagedefinition material subsystem 162 is disposed prior to a segregationmaterial subsystem 164 in the direction of rotation of imaging member12. Image definition material subsystem 162 provides a uniform coating166 of image definition material over reimageable surface 20.Segregation material subsystem 164 forms a pattern of regions 168 ofsegregation material 170 on the surface of photoreceptor 22 aspreviously described. However, in the present embodiment segregationmaterial 170 is strongly attractive to the image definition material.The regions 168 of segregation material are then transferred over imagedefinition layer 166 on reimageable surface 20 such that they sit atopof or diffuse into regions of the image definition material. Theplacement of regions 168 in this embodiment corresponds to regions thatwill not be printed with ink in the final image applied to substrate 14(negative image).

A cleaning subsystem 175 is disposed following segregation materialsubsystem 164 such that the segregation material in regions 168 isremoved from reimageable surface 20. The compositions of segregationmaterial 170 and reimageable surface 20 are such that segregationmaterial 170 easily releases from reimageable surface 20, particularlyas compared to the image definition material. Binding energy of thesegregation material to reimageable surface 20 may be reduced and/orbinding energy of the segregation material to elements of cleaningsubsystem 175 may be increased by electrostatic and/or magnetic controlin the region of cleaning subsystem 173. In the process of removingsegregation material in regions 168, the portion of image definitionmaterial under or within which the segregation material in regions 168was deposited is removed together with the segregation material. Thismay be based on a physical, chemical, or electrostatic attractionbetween the image definition material and segregation material. Theresult is that following cleaning subsystem 175 and before nip 16 in thedirection of rotation of imaging member 12 only image definitionmaterial remains on reimageable surface, and only in the desired patterncorresponding to the pattern ink to be transferred to substrate 14(i.e., a positive image pattern). The image definition material patternmay then be inked by inking subsystem 172, such that ink 174preferentially attaches over regions of image definition materialremaining on reimageable surface 20 following cleaning by cleaningsubsystem 175. The ink image now resident over image definition material166 may then be transferred at nip 16 to substrate 14. Again, some ofthe image definition material may transfer with the ink to substrate 14.This material may evaporate, may provide a desired attribute of thefixed ink image, and so forth, as previously discussed. A correspondingmethod 210 is shown in FIG. 10.

In still another embodiment 220, as illustrated in FIG. 11, an imagedefinition material subsystem 222 is disposed prior to a patterningsubsystem 224 in the direction of rotation of imaging member 12. Imagedefinition material subsystem 222 provides a uniform layer 228 of imagedefinition material over reimageable surface 20. Patterning subsystem224 forms a latent charge pattern on the surface of photoreceptor 22 byselectively exposing regions thereof to light from source 26. The latentcharge pattern corresponds to a positive of the ink image thatultimately is to be transferred to substrate 14. In the presentembodiment, image definition material is not formed over photoreceptor22 as previously described. Rather, as photoreceptor 22 is proximate orcomes into contact with image definition material layer 228, it extractsregions therefrom corresponding to the charge pattern on photoreceptor22. This extraction may be as a consequence of, or enhanced by, a chargeapplied to particles within the image definition material by a chargesubsystem 230, such a charge being of opposite polarity to a charge onphotoreceptor 22 in regions not exposed by light source 26. Thepatterned reimageable surface 20 may then be inked by an inkingsubsystem 46, as previously described, with ink preferentially residingover regions of image definition material remaining on reimageablesurface 20. The ink image may then be transferred to substrate 14, alsoas previously discussed. A corresponding method 240 is shown in FIG. 12.

In one embodiment for use with hydrophilic inks, the image definitionmaterial may be water or a water-based composition. In certainembodiments, the image definition material may be sacrificial, andconsumed in a print cycle, such as by evaporation or removal anddisposition such as by cleaning subsystem 54. Optionally, any imagedefinition material remaining on reimageable surface 20 can be removed,recycled, and reused.

It will therefore be understood that while a water-based solution is oneembodiment of an image definition material that may be employed in theembodiments of the present disclosure, other non-aqueous imagedefinition materials with low surface tension, that are oleophilic, arevaporizable, decomposable, or otherwise selectively removable, etc. maybe employed when used with low polarity inks. One such class of fluidsis the class of HydroFluoroEthers (HFE), such as the Novec brandEngineered Fluids manufactured by 3M of St. Paul, Minn. These fluidshave the following beneficial properties in light of the currentdisclosure: (1) they leave substantially no solid residue afterevaporation, which can translate into relaxed cleaning requirementsand/or improved long-term stability; (2) they have a low surface energy,as required for proper wetting of the imaging member; and, (3) they arebenign in terms of the environment and toxicity. Additional additivesmay be provided to control the electrical conductivity of the imagedefinition material over the photoreceptor. Other suitable alternativesinclude fluorinerts and other fluids known in the art, that have all ora majority of the above properties. It is also understood that thesetypes of fluids may not only be used in their undiluted form, but as aconstituent in an aqueous non-aqueous solution or emulsion as well.

In addition to or as an alternative to fluid-based image definitionmaterials, dry image definition materials may be employed. In theseimplementations, a corresponding development subsystem for dry toner andthe like will be employed. Such dry toner development subsystems may be,for example, of a type employed in xerography, such as cascadedevelopment, magnetic brush development, jumping development, etc., witha similar result of producing an image definition material image on thesurface of the photoreceptor.

In one implementation, the dry image definition material is magnetic,permitting magnetic removal of the image definition material followingtransfer thereof with ink to the substrate, leaving substantially onlythe ink on the substrate surface, or alternatively, magnetic retentionof the image definition material by the reimageable surface followingsplitting of the ink onto the substrate. In the latter case, retentionof the image definition material to the reimageable surface may beassisted by a local magnetic field from a magnetic image definitionmaterial retention subsystem 57 disposed within and partiallycircumferentially around said imaging member and under control ofcontroller 58, shown in FIG. 1. (Other magnetic field producing systemsare also contemplated hereby.) Selective removal of the field can assistwith cleaning of the reimageable surface in preparation for the nextimage writing pass, optionally together with application of a magneticfield by or in association with cleaning subsystem 54 of FIG. 1. Inaddition, magnetic image definition material transferred with ink to asubstrate may be removed post-transfer, such as by a magnetic cleaningsubsystem 59 shown in FIG. 1.

Reimageable surface 20 (FIG. 1) must facilitate the flow of ink onto itssurface with uniformity and without beading or dewetting. Variousmaterials such as silicone can be manufactured or textured to have arange of surface energies, and such energies can be tailored withadditives. Reimageable surface 20, while nominally having a low value ofdynamic chemical adhesion, may have a sufficient surface energy in orderto promote efficient ink wetting/affinity without ink dewetting orbeading.

A system having a single imaging cylinder 12, without an offset orblanket cylinder, is shown and described herein. The reimageable surface20 is made from material that is conformal to the roughness of printmedia via a high-pressure impression cylinder, while it maintains goodtensile strength necessary for high volume printing. Traditionally, thisis the role of the offset or blanket cylinder in an offset printingsystem. However, requiring an offset roller implies a larger system withmore component maintenance and repair/replacement issues, increasedproduction cost, and added energy consumption to maintain rotationalmotion of the drum (or alternatively a belt, plate or the like).Therefore, while it is contemplated by the present disclosure that anoffset cylinder may be employed in a complete printing system, such neednot be the case. Rather, the reimageable surface layer may instead bebrought directly into contact with the substrate to affect a transfer ofan ink image from the reimageable surface layer to the substrate.Component cost, repair/replacement cost, and operational energyrequirements are all thereby reduced.

It should be understood that when a first layer is referred to as being“on” or “over” a second layer or substrate, it can be directly on thesecond layer or substrate, or on an intervening layer or layers may bebetween the first layer and second layer or substrate. Further, when afirst layer is referred to as being “on” or “over” a second layer orsubstrate, the first layer may cover the entire second layer orsubstrate or a portion of the second layer or substrate.

The realization and production of physical devices and their operationare not absolutes, but rather statistical efforts to produce a desireddevice and/or result. Even with the utmost of attention being paid torepeatability of processes, the cleanliness of manufacturing facilities,the purity of starting and processing materials, and so forth,variations and imperfections result. Accordingly, no limitation in thedescription of the present disclosure or its claims can or should beread as absolute. The limitations of the claims are intended to definethe boundaries of the present disclosure, up to and including thoselimitations. To further highlight this, the term “substantially” mayoccasionally be used herein in association with a claim limitation(although consideration for variations and imperfections is notrestricted to only those limitations used with that term). While asdifficult to precisely define as the limitations of the presentdisclosure themselves, we intend that this term be interpreted as “to alarge extent”, “as nearly as practicable”, “within technicallimitations”, and the like.

Furthermore, while a plurality of exemplary embodiments have beenpresented in the foregoing detailed description, it should be understoodthat a vast number of variations exist, and these exemplary embodimentsare merely representative examples, and are not intended to limit thescope, applicability or configuration of the disclosure in any way.Various of the above-disclosed and other features and functions, oralternative thereof, may be desirably combined into many other differentsystems or applications. Various presently unforeseen or unanticipatedalternatives, modifications variations, or improvements therein orthereon may be subsequently made by those skilled in the art which arealso intended to be encompassed by the claims, below.

Therefore, the foregoing description provides those of ordinary skill inthe art with a convenient guide for implementation of the disclosure,and contemplates that various changes in the functions and arrangementsof the described embodiments may be made without departing from thespirit and scope of the disclosure defined by the claims thereto.

What is claimed is:
 1. A variable data lithography system, comprising: aphotoreceptor; a charging subsystem for applying a first electrostaticcharge to said photoreceptor; an exposure subsystem disposed forselective exposure of said photoreceptor to thereby form an exposurepattern from regions that are exposed and unexposed by said exposuresubsystem on a surface of said photoreceptor, said exposure enablingaltering the electrostatic charge on said photoreceptor to therebydefine regions of said photoreceptor having a first electrostatic chargestate and a second electrostatic charge state; an image definitionmaterial subsystem disposed proximate said photoreceptor for selectivelyapplying an image definition material substantially over regions of saidphotoreceptor having said first electrostatic charge state and not overregions having said second electrostatic charge state to thereby form animage definition material image on a surface of said photoreceptorcorresponding to said exposure pattern; an imaging member having areimageable surface formed thereover, disposed proximate saidphotoreceptor such that said image definition material selectivelyapplied over said photoreceptor is transferred over said reimageablesurface, forming regions of image definition material separated byregions of no image definition material on said reimageable surface, andthereby transferring said image definition material image between saidphotoreceptor and said reimageable surface; an inking subsystem forselectively applying ink over said reimageable surface such that saidink preferentially occupies regions over said image definition materialon said reimageable surface to thereby form an inked image over saidreimageable surface; and an image transfer subsystem for transferringthe ink over said image definition material to a substrate to therebytransfer said inked image from said reimageable surface to saidsubstrates wherein said regions of said photoreceptor having a firstelectrostatic charge state have a first charge polarity, and furtherwherein said image definition material subsystem is configured such thatimage definition material applied thereby over said photoreceptorcomprises electrostatically charged particles having a second chargepolarity, said first charge polarity being opposite said second chargepolarity, wherein said image definition material comprises a dampeningfluid, said dampening fluid comprising a carrier fluid in which aredisposed said electrostatically charged particles.
 2. The variable datalithography system of claim 1, wherein said first electrostatic chargestate corresponds to regions not exposed by said exposure subsystem, andsecond electrostatic charge state corresponds to regions exposed by saidexposure subsystem.
 3. The variable data lithography system of claim 1,wherein said image definition material subsystem further comprises acharge application subsystem for applying said electrostatic chargehaving said second charge polarity to said particles.
 4. The variabledata lithography system of claim 1, wherein said carrier fluid iselectrically insulative.
 5. The variable data lithography system ofclaim 1, wherein said particles are organic polymers.
 6. The variabledata lithography system of claim 1, wherein said particles are selectedfrom the group consisting of: inorganic magnetic nanoparticles andinorganic dielectric nanoparticles.
 7. The variable data lithographysystem of claim 1, further comprising a charge application devicedisposed proximate said imaging member and configured to apply anelectrostatic charge of said first polarity to said imaging member suchthat said particles are electrostatically attracted to said reimageablesurface during transfer thereof from said photoreceptor to saidreimageable surface.
 8. The variable data lithography system of claim 1,further comprising a charge application device disposed proximate saidimage transfer subsystem and configured to apply an electrostatic chargeof a polarity opposite that of said first electrostatic charge to anelement of said image transfer subsystem such that said particles, butnot said ink, are electrostatically rejected in a region at which saidink transfers from said reimageable surface to said substrate.
 9. Thevariable data lithography system of claim 1, further comprising aviscosity control subsystem disposed proximate said photoreceptorfollowing said image definition material subsystem in a direction ofmotion of said photoreceptor for controlling the viscosity of imagedefinition material on the surface of said photoreceptor prior totransfer of said image definition material to said imaging member. 10.The variable data lithography system of claim 9, wherein said viscositycontrol subsystem comprises a heating element configured to direct heatenergy toward said photoreceptor.
 11. The variable data lithographysystem of claim 1, further comprising a segregation material subsystemdisposed proximate said reimageable surface and between saidphotoreceptor and said inking subsystem in a direction of motion of saidimaging member, said segregation material subsystem configured toselectively deposit segregation material substantially in said regionsof no image definition material over said reimageable surface.
 12. Thevariable data lithography system of claim 1, further comprising asegregation material subsystem disposed proximate said photoreceptor andbetween said image definition material subsystem and a point at whichsaid image definition material is transferred to said reimageablesurface in a direction of motion of said imaging member, saidsegregation material subsystem configured to selectively depositsegregation material substantially in regions of no image definitionmaterial over said photoreceptor, and further wherein said reimageablesurface is configured to receive both said image definition material andsaid segregation material in a pattern substantially corresponding tosaid image definition material image with said segregation materialsubstantially occupying said regions of no image definition materialover said reimageable surface.
 13. The variable data lithography systemof claim 1, wherein said image definition material comprises magneticparticles disposed in a carrier fluid.
 14. The variable data lithographysystem of claim 13, further comprising a cleaning subsystem, disposedproximate said imaging member and following said image transfersubsystem, for cleaning, at least in part by way of magnetic attractionof said magnetic particles, residual image definition material from saidreimageable surface.
 15. A variable data lithography system, comprising:a photoreceptor; a charging subsystem for applying a first electrostaticcharge having a value and a first charge polarity to said photoreceptor;an exposure subsystem disposed for selective exposure of saidphotoreceptor to thereby form an exposure pattern from regions that areexposed and unexposed by said exposure subsystem on a surface of saidphotoreceptor, said exposure altering the electrostatic charge on saidphotoreceptor to thereby define regions of said photoreceptor having afirst electrostatic charge state corresponding to regions not exposed bysaid exposure subsystem and a second electrostatic charge statecorresponding to regions exposed by said exposure subsystem; an imagedefinition material subsystem disposed proximate said photoreceptor forselectively applying an image definition material layer substantiallyover regions of said photoreceptor having said first electrostaticcharge state and not over regions having said second electrostaticcharge state to thereby form an image definition material image on asurface of said photoreceptor corresponding to said exposure pattern,said image definition material comprising a dampening fluid, saiddampening fluid comprising a carrier fluid comprising anelectrostatically insulative carrier fluid in which is disposedelectrostatically charged particles having a second charge polarity,said first charge polarity being opposite said second charge polarity;an imaging member having a reimageable surface formed thereover andhaving a second electrostatic charge of a value greater than said valueof said first electrostatic charge, disposed proximate saidphotoreceptor such that said image definition material selectivelyapplied over said photoreceptor is transferred to said reimageablesurface, forming regions of image definition material separated byregions of no image definition material on said reimageable surface, andthereby transferring said image definition material image from saidphotoreceptor to said reimageable surface; an inking subsystem forselectively applying ink over said reimageable surface such that saidink preferentially occupies regions of image definition material on saidreimageable surface to thereby form an inked image corresponding to saidimage definition material image over said reimageable surface; and animage transfer subsystem for transferring the ink occupying said regionsof image definition material on said reimageable surface to a substrateto thereby transfer said inked image from said reimageable surface tosaid substrates wherein said regions of said photoreceptor having afirst electrostatic charge state have a first charge polarity, andfurther wherein said image definition material subsystem is configuredsuch that image definition material applied thereby over saidphotoreceptor comprises electrostatically charged particles having asecond charge polarity, said first charge polarity being opposite saidsecond charge polarity.